Among the many insecticidal compounds, the phthalimidothiophosphates have reached a relatively high degree of commercial success. These compounds are toxic to a large number of insect pests at concentrations varying with the resistance of the insect. Some of these compounds are described in U.S. Pat. No. 2,767,194, specifically N-(mercaptomethyl) phthalimide S--(O,O-dimethylphosphorodithioate). The endeavor to extend the usefulness of the thiophosphates by increasing their effectiveness and lowering their cost has led to extensive studies on another class of biologically active chemicals, customarily referred to as activators.